Suppression of self-inductive obstruction in electromagnetic apparatus



(No Model.) S. D. FIELD. SUPPRESSION 0F SELF INDUGTIVB OBSTRUGTION IN ELECTRMAGNETI V APPARATUS.

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15 Y The object of the UNITED STAT-Es j 'lijATENr OFFICE.

STEPHEN D. FIELD, OF STOOKBRIDGE, ASSIOYNOR TO THE AMERICAN BELL TELEPHONE OOMPANY,`OF BOSTON, MASSACHUSETTS.

SUPPRESSION F SELF-INDUCTIVE OBSIRUCTION IN ELECTROMAGNETIC APPARATUS.

SPECIFICATION forming part of Letters Patent No. 530,516, dated December 11, 1 894.

Application filed July 24, 1894- Serial No. 518,479. (No model.) i A To all whom t may concern: i Be it known that I, STEPHEN D. FIELD, residing at Stockbridge, in the county of Berkshire and State of Massachusetts, have in-p vented certain Improvements in the Suppression of Self-Inductive Obstruction in Electro` invention is to provide means whereby an electro-magnet may be so constructed as to be practically neutral to the reactance or obstructive action due to the, self-induction of conductors when closely` coiled about a magnetic core as in ordinary electromagnets, without at ajllimpairing their efficiency. This self inductive obstruction opposesthe passage of all changing currents, and;

is avery serious obstacle to the transmission 2 5 of rapidly varying currents such as voice currents, or those employed in vibrator-y telegraphy; whether as developed in the transmitting and receiving or translating instruments themselves, or as developed in instruments located intermediately in the circuit as at way stations, and its neutralization therefore isa matter of considerable importance. y y

It is a wellknown fact that the self induc- 3 5 tion and electro-static capacity of an electric circuit may be reciprocally utilized each to` counteract the adverse influence ofthe other; and in suppressing the injurious action of self induction it is a familiar practice to associate condensers with the circuit in order that their eects,-which considered alone would act adversely,may beavailable to oppose and neutralize the equally but different effects of magnetic reactance.

In Letters Patent No. 91,163, granted to me February 7, 1893, is disclosed one mode of accomplishing the desired result, vizz-by means of condensers attached at intermediate points in a helix or series of helices.

t In my present inventionl attaina like'result by causing the insulated conducting wire oan electromagnetic. helix to serve as one plate ot a condenser, of which a strip or ribbonof tinfoil or other similar conductor interposed between the layers of the said wind- 5 5 ing, forms the remaining plate; this ribbon being thereby brought into a position where' it will havereciprocal inductive relations with the associated convolutions of Wire.

i My invention further consists in an electro- 6o magnet having an associated incomplete electro-static shunt composed of a conductor extending between the layers of the magnet winding; in an electro-magnet which is also a condenser, the windingthereof forming one condenser plate, and aseparate conductor interposed between the' layers ot' said winding constituting the other condenser plate; and in a magneto telephone which combines its ordinary elements with the incomplete elec- 7o trostatic shunt circuit, whose conductors are interposed between the layers ot the telephone coil winding.

Many modications may of course be arrangedwithout any departure from the spirit 7 5 of the invention, as is indeed indicated in the drawings whichaccompany and illustrate the specification.

In adapting my invention to a translating or other instrument such"` as a speaking tele- 8o phone, a bell magnet or a relay, I sometimes employ a series of conducting plates, or strips,

connected in parallel, and placed between the several layers of the coil or helix conductor; or alternatively, I employ a number of such plates connected in sequence in such a way that the chargesand discharges which may be regarded as an induced current, will circulate in them around the magnet core in the same direction as that circulating in the coils of 9o the magnet helix; or, if desired, the conducting piates or strips may be connected in series,`but in' such a manner that the induced currentwill circulate in a direction opposite to that of the line current.

In the drawings, Figure l shows a cross section of a telephone with which the present invention is associated. Figs. 2, 4, 6 and 8 rep- `resent cross sections in plan, of electro-magnetic coils fitted with the electrostatic attachroo ment in accordance with my invention; and

Figs. 3, 5, 7, and 9, are theoretical diagrams representing the electrical arrangement of the said cross-sections respectively. Fig. 10 indicates an application of my invention to an ordinary polarized bell, and Fig. ll to a relay.

In Fig. 1, T is a magneto telephone with the usual magnet M, with core m, helix H, dia-l phragm D, and cap C, and its coil terminals 3 and 4 extend within the case to the binding screws p and p2.

In the coil or helix lil, c represents the winding of wire and e the several interposed p0rtions 0f the inductive circuit strip.

Figs. 2 and 3 are different expressions of the same organism. They show an arrangement wherein the inductive circuit plates e, e2, e3, dac., are all connected in multiple with the inside terminal of the helix, the point of union being shown at g, and the plates being interposed betwen the several layers c c2 and c3, of the continuous conductor extending from 3 to 4, through the helix. An exceedingly minute vibration is required to traverse but a very few turns of wire before finding an inductive passage to the nearest interposed inductive circuit plate; while a more prolonged impulse will find its circuit either through all of the wire of the helix to the other terminal, or through a greater or lesser portion of the wire to two or more of the interposed plates.

In Figs. 4. and 5, the interposed plates c are serially connected and their connection is such that the cnrrents inductively developed in them fiow around the core m, in the same direction as the line current flowing in the continuous conductors c.

In Figs. 6 and 7 the connection of the inductive circuit strip is made at the outer terminal of the continuous conductor, and the two conductors are relatively arranged in such a manner that the plates e of the said strip are in sequence, while the induced currents will in their effect oppose that of the line currents circulating in the helix conductor c.

The arrangement shown in Figs. 8 and 9 shows the several concentric plates or strips e connected in series as in the two previous plans, but each concentric layer is so connected that the induced current ows in it around the core in a direction opposite to that fiowing in its associate strip on either side.

Experiment proves that the reactance of the electro-magnetic coil is much reduced by the neutralizing operation of any of these plans of constructing the associated inductive circuit.

In telephone circuits which have intermediate or way stations the impedance of the bell magnets at such way stations has been so high, that voice currents have found much difficulty in passing them, but if such bell magnets are provided with the means indicated herein, as shown in Fig. 10, the difficulty is much reduced, and the said voice currents or other rapidly vibrating currents, may then find ready passage through the said electro magnets.

The same is true with respect to telegraph lines; and currents varying at high frequencies, can be transmitted easily and without distortion through relay magnets to which as in Fig. 11 this invention has been applied. Any of the circuit arrangements shown in Figs. 2, 4, 6 or 8 may be employed in connec tion with the bell and relay of Figs. 10 and l1 or with any electro-magnet. Thus by the application of my invention to electro-magnets,and the consequent neutralization of the self induction, and virtual transformation of such magnets into condensers, vibratory currents, or 'currents of frequent variation or change,are enabled to pass throughtheir coils with great facility, while the working efficiency of the coils or helices themselves, or the facility with which they can act upon, or be acted upon by their magnetic cores, remains practically unimpaired.

I am aware that it is not new to attempt the elimination of the effects of self induction of coiled wires by means of cylinders of metal interposed between the layers of such coiled wire, but in all such cases, of which I have knowledge each cylinder so interposed, forms a closed circuit around the core of the magnet; and such closed circuit affords a path for currents induced by line currents passing through the wire of the surrounding helix; but these currents at all times necessarily delay magnetic changes, since when the main current is rising, the direction of the induced current is in opposition thereto, tending to weaken or make sluggish the effect thereof; while when the main current is falling the induced current is of like direction and tends to perpetuate the effect of the said main current. This delay renders such devices inefficient, when used in connection with apparatus intended to manifest currents of high frequency of vibration-that is to say, in such devices, self-induction is eliminated at the expense of the working eiciency of the magnet in which the device is incorporated; being accomplished by dynamic or magneto electric induction, in contradistinction ot static induction which is employed in the device described in this specification.

Having now fully described my invention, I claim- 1. In an electro magnet, the combination with the helices or convolutions thereof, of a conductor in reciprocal inductive relation with the wires composing said coils or helices, for the purpose of suppressing the reactance or self induction of the magnet, substantially as described.

2. The combination with an electro-magnet, of an associated incomplete electro-static shunt or inductive circuit, connected with one of its terminals, and having branches or extensions interposed between the several layers of its convolntions, substantially as described.

3. A combined electro magnet and condenser the condenser having for one of its plates the winding of the electro-magnet, and

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for the other a strip or ribbon of tinfoil or like conductor interposed between the several layers of the said winding in inductive relation thereto. 1

4. The combination in a magneto telephone, with the magnetic core, and its surrounding helix, of an associated incomplete inductive circuit interposed continuously between the several layers of the saidhelix, substantially as described. y

5. A magneto telephone having conducting strips, ribbons or plates branching or extending from one of the terminals of its helix,l and interposed between the several layers of the winding of said helix, whereby the electro-static capacity of said helix is increased.

STEPHEN D. FIELD.`

. Witnesses:

THOMAS D. LooKwooD, CEAS. E. EVANS. 

